Predicting CO2 solubility in aqueous N-methyldiethanolamine solutions with ePC-SAFT

In this work, electrolyte PC-SAFT equation of state developed in 2005 with the parameters from Held et al. [Chem. Eng. Res. Des. 92 (2014) 2884–2897] has been applied to predict the solubility of CO2 in aqueous N-methyldiethanolamine (MDEA) solutions. The considered temperature range was 313–413 K, MDEA weight fractions up to 0.32 (related to the binary water/MDEA system) and loadings of up to 1.32 (mole CO2/mole MDEA).In order to predict CO2 solubilities, the reaction equilibria and phase equilibria were solved simultaneously by explicitly accounting for the electrolyte species being present in the system: H+, OH−, HCO3−, CO32− and MDEAH+. The pure-component parameters for the molecular components (H2O, CO2, MDEA) and for all ions except MDEAH+ were already available in the literature. MDEAH+ pure-component parameters were inherited from MDEA, and the charge was explicitly accounted for in ePC-SAFT. Binary parameters were applied only for the pairs H2O/CO2, H2O/ions, and H2O/MDEA. The deviations between experimental and ePC-SAFT modeled CO2 solubility in aqueous MDEA solutions was 19.82% for a temperature range of 313–413 K, a MDEA weight fractions of 0.19, and CO2 loadings of up to 1.3 (mole CO2/mole MDEA). As binary parameters have not been adjusted to experimental CO2 solubility data in aqueous MDEA solutions, these results can be considered as predictive.